1. Field of the Invention
The invention relates to a magnetically navigable device with at least one associated magnet element which has a greater extent in one direction than at right angles thereto. The device can be assigned a central axis which points in this direction in which the magnet element extends. Such a magnetically navigable device can be found in DE 101 42 253 C1.
2. Description of the Related Art
In medicine, use is made of probe-like devices such as endoscopes or catheters which are inserted into a proband through incisions or body orifices and can be displaced externally in the longitudinal direction and hence can be navigated in one dimension. Optical fibers permit visual inspection, with control wires being able to be used to swivel an endoscope tip and hence the viewing direction. It is thus possible to produce devices for biopsies, in particular. However, the probe-like devices used in this context have only limited navigability, particularly at branch points, which means that contactless exertion of force from outside might entail an expansion of the field of application. Such an exertion of force can be brought about magnetically.
The publication “IEEE Transactions on Magnetics”, Vol. 32, No. 2, March 1966, pages 320 to 328 and U.S. Pat. No. 5,125,888 A discloses a magnet coil system for such contactless magnetic probe control. The coils in the system can be used to generate variable field directions and field gradients, in order to guide or move a magnetic probe device, such as a catheter with magnetic material or magnetic implants, in a body to be examined, for example a human body, for the purposes of therapy.
WO 96/03795 A1 describes a method with additional pulse coils which can be used for moving a magnetic probe device in steps by precisely defined current pulses under computer control.
“Video capsules” used for inspecting the digestive tract are also known, by way of example, from the journal “Gastrointestinal Endoscopy”, Vol. 54, No. 1, 2001, pages 79 to 83. In this context, however, the video capsule is moved by the natural intestinal movement; that is to say that the movement and the viewing direction of the capsule are purely random.
DE 101 42 253 C1 cited at the outset discloses a corresponding, largely cylindrical video capsule which thus has a pronounced extent in the direction of a longitudinal axis. This capsule is equipped with a bar magnet and also with video apparatuses and other intervention apparatuses. Forces for navigation are intended to be exerted on the bar magnet by an external magnet coil system (not described in more detail). Mention is made of a freely suspended “helicopter mode” with external control by a 6D mouse, feedback of the force via the mouse and positional feedback by a transponder. The known video capsule's bar magnet extends centrally along the axis, which means that the common center of gravity of the video capsule and of the bar magnet is situated on this axis. It is thus not possible to control the degree of rotational freedom about the longitudinal axis magnetically, however. The consequence of this is that a prescribed position, for example the “top” position, on a transmitted video image does not match the corresponding “top” position in a co-ordinate system in the video capsule.